I will tell you one story.Please do not judge me.I have no idea why i picked a Doll as my imaginary friend.Ah yes, Transformers!
When I was very young-so young that I don't remember creating her.I came up with an imaginary friend of my own.But she truly was my best friend for a while.I was in pre-school.I told my friend that I have a doll which is like a robot..She would play games with me . I said it is too real and that we're like sisters and we tell each other secrets. It help me and always eats my food for me , will do my homework and will do the house hold work so I don't have to.Every day she watch over me and protect me....Blah blah blah. Daily I told her about my doll. Still I don't know whether she believed these stories or not.If i met her anytime in my life,I definitely will ask her.
Eventually my imaginary doll left me but of course I remember her...still I try and figure out where such a young kid would think up something like that :)